A passive optical network (PON) is one system for providing network access over “the last mile.” The PON is a point to multi-point network comprised of an optical line terminal (OLT) at the central office, an optical distribution network (ODN), and a plurality of optical network units (ONUs) at the customer premises. In current PON systems, downstream data is broadcast to all of the ONUs, while upstream data is sent to the OLT using time division multiple access (TDMA) techniques. For instance, PON systems can broadcast downstream data at about 2 Gigabits per second (Gbps) using a wavelength at about 1490 nanometers (nm). The PON systems can also provide about 1 Gbps of transmission bandwidth for upstream data, which uses a wavelength of about 1310 nm.
Future PON systems are expected to deliver larger transmission bandwidths for downstream and upstream data than those delivered by the current PON systems. In addition, the future PON systems may transmit downstream and upstream data using more wavelengths. The future PON systems will be expected to coexist with the existing PON systems to reduce capital and operating costs. Such PON systems may be required to share the spectral window and avoid data collisions with the existing PON systems.